Agar (or libAgar)
is a cross-platformGUI toolkit.
Agar provides a base framework and a set of widgets from which applications
can be built.

Agar applications work natively under
X11,
Windows,
MacOS X,
SDL
and others.
Agar takes advantage of hardware acceleration when it is available.
Agar may also attach to an existing SDL or
OpenGL context and operate as
a self-contained windowing GUI for the application.
Agar can be compiled with zero dependencies (although
FreeType
is recommended for font quality).
Agar focuses on performance, efficiency and extensibility. The Agar API
is, unless documented otherwise, fully thread-safe.

Deriving or creating new widgets is simple. The set of widgets built into
the library are intended to meet the most common needs of applications,
but Agar's class registration interface allows new widgets to be deployed
quickly.
Examples of separate libraries which implement Agar widgets for specific
fields include
FreeSG,
Edacious,
Agar-Math,
Agar-VG and
Agar-Dev.

Agar is also extensible at the low-level.
The low-level API is fully documented such that modular drivers can be
written which enable Agar application to run under novel platforms and
graphics systems.

Agar is free software. Its source code is freely usable and re-usable by
everyone under a BSD license, which allows
use in commercial applications free of charge.
The best available version is
1.5.0.